JP2007245895A - Motor drive controller for electric motor type four wheel drive vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a voltage from being abnormally increased, resulting from that a motor torque command value sharply decreases according as a speed increases, while a motor torque command value is limited to the upper limiting torque that can be output. <P>SOLUTION: Characteristics of motor revolution speed regions Nm1 to Nm2 such that the change rate of a motor outputable upper limit torque for a motor revolution speed Nm is the highest, and that abnormal voltage increase is easily generated resulting from that the motor torque command value sharply decreases according, as the speed increases under the limit of the motor torque command value, based on this are changed to the real line characteristics that change ratio is smooth so that virtual upper limit motor torque can be set, and the other characteristics are made the same as an upper limit torque line that can be output so that an allowable upper limit torque line can be obtained. When the motor torque command value is to be limited, the motor torque command value is limited, based on the allowable upper limit torque line shown with a solid line, instead of the outputable upper limit torque line, shown by a wavy line under motor revolution acceleration at which abnormal voltage increase is generated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric motor type four-wheel drive vehicle in which one of front and rear wheels is driven by a main power source such as an internal combustion engine (engine) and the other wheel is driven by power from an electric motor, and in particular, torque of the electric motor. The present invention relates to a technique for preventing an abnormal voltage increase when the command value is rapidly reduced by being limited so as not to exceed the output possible upper limit torque for each motor rotation speed.

  In addition to main drive wheels driven by power from a main power source such as an internal combustion engine (engine), an electric motor driven by power from an electric motor that responds to power generated by a generator coupled to the main power source Conventionally, as an electric motor type four-wheel drive vehicle including a drive wheel, there is a vehicle as described in Patent Document 1, for example.

This vehicle drives the front two wheels (or the rear two wheels) with an engine, and the rear two wheels (or the front two wheels) can be driven by an electric motor. To directly drive the electric motor.
In the drive control of the electric motor, the torque command value of the electric motor is determined according to the driving state of the vehicle, and the motor energy is commanded by controlling the electric energy from the generator to the electric motor to correspond to this. Achieve the desired purpose as a value.
Japanese Patent Application Laid-Open No. 07-231508

By the way, while controlling the motor torque command value so that the actual motor torque becomes this command value, the power for driving the motor also decreases sharply, and the generated power of the generator driven by the engine suddenly surplus Thus, the surplus power that has rapidly increased causes an abnormal increase in voltage.
There is a concern that such an abnormal increase in voltage not only adversely affects the control system of the electric motor type four-wheel drive vehicle but also causes troublesome operation of a safety device for preventing this adverse effect.

In order to avoid this concern, it is also possible to slowly decrease the motor torque command value if an abnormal voltage increase occurs while monitoring the power generation status of the generator while the motor torque command value is decreasing. But
As explained below, when it is necessary to limit the motor torque command value due to a hardware limit or the like, the motor torque command value must be rapidly reduced. The restriction must be prioritized, the above measures cannot be used, and an abnormal increase in voltage due to surplus power cannot be avoided.

That is, as illustrated in FIG. 10, the electric motor has an outputable upper limit torque for each rotation speed Nm (corresponding to the vehicle speed VSP), and a command value exceeding this is given as the motor torque command value of the electric motor. However, the electric motor cannot output the corresponding torque, which is not preferable in terms of control.
Therefore, when the motor torque command value is a torque value exceeding the output possible upper limit torque line illustrated in FIG. 10, the motor torque command value is generally limited to the output possible upper limit torque.

  However, while the motor torque command value is limited, the rate of change of the maximum outputable torque with respect to the motor rotation speed Nm (vehicle speed VSP) is relatively large. For example, the motor rotation speed in the motor rotation speed range between Nm1 and Nm2 shown in FIG. When Nm (vehicle speed VSP) increases, the motor torque command value decreases at a rapid rate, and this sudden decrease in motor torque command value causes surplus power generated by the generator, resulting in abnormal voltage. Cause a rise.

  In order to solve this problem, even if the motor torque command value is decreased slowly, the limitation of the motor torque command value based on the hardware limit must be prioritized. Thus, the above-mentioned countermeasure of slowly decreasing the voltage cannot be used, and the problem relating to the abnormal voltage increase due to the sudden decrease in the motor torque command value cannot be avoided.

The present invention provides a hardware limit map used for limiting a motor torque command value so that even if the motor torque command value is limited based on the hardware limit, the rate of decrease does not become so steep as to cause an abnormal voltage increase. If you operate
Based on the fact recognition that the motor torque command value can be prevented from abruptly decreasing during the limit of the motor torque command value based on the hardware limit, and the above-mentioned problem related to the abnormal increase in voltage can be avoided,
It is an object of the present invention to propose a motor drive control device for an electric motor type four-wheel drive vehicle that embodies this idea and can solve the conventional problems.

For this purpose, the motor drive control device for an electric motor type four-wheel drive vehicle according to the present invention has the following configuration as described in claim 1.
First of all, the premise of the electric motor type four-wheel drive vehicle is
A main drive wheel driven by power from a main power source;
An electric motor drive wheel driven by power from an electric motor that responds to power generated by a generator coupled to the main power source,
The motor torque command value of the electric motor is limited so as not to exceed an outputable upper limit torque for each motor speed.

The present invention, in such an electric motor type four-wheel drive vehicle,
When the rate of decrease in the motor torque command value due to the limitation of the motor torque command value is a sudden decrease that causes an abnormal increase in voltage due to the surplus of the generated power, the output possible upper limit for the motor rotation speed The motor torque command value is limited by using a virtual upper limit torque having a gentler change rate than the torque change rate instead of the output possible upper limit torque.

According to the motor drive control device of the present invention,
When the rate of decrease in the motor torque command value due to the limitation of the motor torque command value is a sudden decrease that causes an abnormal voltage increase, the virtual torque upper limit torque is used in place of the outputable upper limit torque. Since the change rate of the virtual upper limit torque with respect to the motor rotation number is more gradual than the change rate of the output possible upper limit torque with respect to the motor rotation number,
While the motor torque command value is being limited, it is possible to mitigate that the rate of decrease becomes so steep that an abnormal voltage increase occurs. The adverse effect on the control system can be avoided and the troublesome operation of the safety device for preventing this adverse effect can be eliminated.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
FIG. 1 schematically shows a drive system of an electric motor type four-wheel drive vehicle including a motor drive control device according to an embodiment of the present invention.
In this embodiment, this vehicle is a front engine / front wheel drive vehicle (F / F vehicle) driven by an engine (internal combustion engine) 2 with the left and right front wheels 1L and 1R as the main power source, and the left and right rears. A so-called electric motor type four-wheel drive vehicle in which the wheels 3L and 3R can be driven by a rear wheel drive motor 4, which is an electric motor, as required.

As usual, the output of the engine 2 is increased according to the degree to which the driver depresses an accelerator pedal (not shown) as an accelerator operating means.
The engine 2 is drivably coupled to the left and right front wheels (main drive wheels) 1L and 1R via a transaxle in which the automatic transmission 5 and the differential gear device 6 are configured as an integral unit. It is assumed that the vehicle is transmitted to the left and right front wheels 1L and 1R via the differential gear device 6 and used for traveling of the vehicle.

  Next, a rear wheel drive system by the electric motor 4 will be described. This includes a dedicated generator 8 driven via an endless belt 7 by a part of the output torque of the engine 2, and the generator 8 The engine is driven at a rotation speed obtained by multiplying the rotation speed of 2 by the belt pulley ratio, and a power generation load corresponding to the field current Ifh adjusted by the four-wheel drive controller 9 is applied to the engine 2 to generate power corresponding to the load torque. To do.

The electric power generated by the generator 8 is supplied to the rear wheel drive motor 4 through the relay 11 through the power line 10.
The relay 11 is also controlled by the command from the controller 9 when the power line 10 is cut off when the generator 8 becomes poorly controlled, or when the rear wheel drive is unnecessary and the controller 9 does not apply a power generation load to the generator 8. Since there is some power generation by the permanent magnet, the power line 10 is cut off so as not to be supplied to the motor 4.

  The drive shaft of the rear wheel drive motor 4 is coupled to the differential gear device 14 of the left and right rear wheels (electric motor drive wheels) 3L and 3R via the speed reducer 12 and the 4WD clutch 13 incorporated therein, and the output of the motor 4 If the torque is increased by the gear ratio by the speed reducer 12 and the 4WD clutch 13 is engaged, the increased torque is distributed and output to the left and right rear wheels 3L and 3R by the differential gear device 14.

The four-wheel drive controller 9 also controls the engagement / release of the 4WD clutch 13 and the rotation direction / drive torque of the electric motor 4.
In the control of the electric motor 4, the controller 9 will describe the motor torque command value of the electric motor 4 corresponding to the target driving force of the left and right rear wheels (electric motor driving wheels) 3L, 3R determined according to the vehicle operating state, as necessary. The motor drive torque is controlled to match this command value by adjusting the field current Ifm to the electric motor 4, and the motor rotation direction is controlled by the direction of the field current Ifm.

In addition to inputting the signal from the four-wheel drive switch 21 to the four-wheel drive controller 9 for performing the above-described control of the motor 4, the generator 8, the relay 11, and the 4WD clutch 13,
Signals from the wheel speed sensor group 22 for individually detecting the wheel speeds (front wheel speeds) V _WFL and V _WFR of the left and right front wheels 1L and 1R and the wheel speeds (rear wheel speeds) V _WRL and V _WRR of the left and right rear wheels 3L and 3R When,
A signal from the motor rotation sensor 23 for detecting the rotational speed Nm of the rear wheel drive motor 4,
A signal from an accelerator opening sensor 25 that detects an accelerator pedal depression amount (accelerator opening) APO is input.

The four-wheel drive controller 9 determines whether the four-wheel drive is necessary and automatically performs the motor four-wheel drive while the driver is turning on the four-wheel drive switch 21 as described later.
While the driver is turning off the four-wheel drive switch 21, the two-wheel drive by only the engine drive of the front two wheels is continuously performed.

Hereinafter, basic four-wheel drive control performed by the controller 9 will be described.
First, by the process shown in FIG. 2, surplus torque of the engine 2 that causes the driving (acceleration) slip of the front wheels 1L and 1R that are the main driving wheels (engine driving wheels) is calculated.
In step S1, from the average front wheel speed Vwf that can be obtained from the front wheel speeds V _WFL and V _WFR detected by the wheel speed sensor group 22, the average after that that can be obtained from the rear wheel speeds V _WRL and V _WRR that are also detected by the wheel speed sensor group 22 By subtracting the wheel speed Vwr, the acceleration slip amount ΔVf of the left and right front wheels 1L and 1R which are the main drive wheels is obtained.

In the next step S2, it is determined whether or not an acceleration slip has occurred depending on whether or not the acceleration slip amount ΔVf of the left and right front wheels 1L and 1R is a predetermined value, for example, 3 km / h or more.
When it is determined that the acceleration slip amount ΔVf is less than 3 km / h, the control is terminated as it is because no acceleration slip has occurred and there is no surplus of engine output.

When an acceleration slip is determined in step S2 that the acceleration slip amount ΔVf is 3 km / h or more, it is necessary to suppress the surplus torque of the engine that generates the acceleration slip of the front wheels 1L and 1R, that is, the acceleration slip in step S3. The absorption torque T (ΔVf) is calculated by T (ΔVf) = K1 × ΔVf.
K1 is a gain obtained through experiments or the like.

In the next step S4, the current load torque Tg of the generator 8 is obtained. In step S5, the current generator load torque Tg and the surplus torque T (ΔVf) are added together to obtain the target power generation load of the generator 8. Find the torque Th.
In step S6, the motor speed VSP that can be obtained from the wheel speeds V _WFL , V _WFR , V _WRL , V _WRR is a motor overspeed vehicle speed that is a lower limit value of the vehicle speed range in which the motor 4 is overrotated when the 4WD clutch 13 is engaged ( For example, check whether it is less than 30km / h).

If the vehicle speed VSP is equal to or higher than the motor overspeed vehicle speed, the motor 4 is overrotated and its durability is lowered. Therefore, the control is terminated as it is so that the four-wheel drive is not performed, but the vehicle speed VSP is less than the motor overspeed vehicle speed. Then, in step S7, the maximum load torque Thmax of the generator 8 is obtained.
Next, in step S8, it is checked whether or not the target power generation load torque Th (step S5) of the generator 8 is greater than or equal to the maximum load torque Thmax, and if so, the limit in which the target power generation load torque Th can be realized by setting Th = Thmax in step S9. If Th <Thmax, the control is terminated and the target power generation load torque Th is set to the value as obtained in step S5.

In FIG. 2, the method of obtaining the target power generation load torque Th of the generator 8 only when the engine drive wheels 1L and 1R generate an acceleration slip has been described.
Even if the engine drive wheels 1L and 1R may be accelerated and slipped, or when the engine drive wheels 1L and 1R are in a low speed state below a predetermined level, the target power generation load torque Th of the generator 8 is driven in order to realize the four-wheel drive of the electric motor. According to

The controller 9 controls the generator 8 and the motor 4 by the control program of FIG. 3 based on the target power generation load torque Th of the generator 8 obtained as described above.
In step S11, it is checked whether or not there is a power generation request depending on whether or not the target power generation load torque Th of the generator 8 is positive.
If there is no power generation request, the control is terminated, so that the power generation load of the generator 8 is not applied to the engine 2, and the 4WD clutch 13 is in a released state.
If there is a power generation request, in step S12, the target motor field current Ifm is calculated from the motor rotation speed Nm based on the scheduled map.
Although not shown, at the same time, when the input / output rotational speeds of the 4WD clutch 13 coincide with each other, the 4WD clutch 13 is engaged so that the rotation of the motor 4 can be transmitted to the rear wheels 3L and 3R.

Here, as shown in step S12, the target motor field current Ifm with respect to the rotational speed Nm of the motor 4 is set to a constant predetermined current value when the motor rotational speed Nm is equal to or smaller than the predetermined rotational speed, and the motor rotational speed beyond that is determined. When the number is reached, the field current Ifm of the motor 4 is reduced by a known field weakening control method.
The reason for this is that when the motor 4 rotates at a high speed, the motor torque decreases due to the increase of the motor back electromotive force E. Therefore, when the motor rotation speed Nm exceeds a predetermined value, the field current Ifm of the motor 4 is decreased and reversed. This is because the current flowing through the motor 4 is increased by reducing the electromotive voltage E so that the required motor torque Tm can be obtained.

Next, at step S13, the back electromotive force E of the motor 4 is calculated from the target motor field current Ifm and the rotation speed Nm of the motor 4 obtained as described above, based on a predetermined map.
Further, in step S14, a corresponding motor torque command value tTm is calculated based on the power generation load torque Th described above, and is basically limited as described above with reference to FIG. After limiting based on the allowable upper limit torque map corrected as described later with respect to 9, the target motor field current Ifm corresponding to the motor torque command value tTm is commanded to the electric motor 4, and the electric motor 4 receives the motor torque command value tTm. The torque corresponding to is output.

In step S15, a target armature current Ia that is a function of the motor torque command value tTm and the target motor field current Ifm is calculated.
Thereafter, in step S16, the target voltage V of the generator 8 is obtained from the target armature current Ia, the total resistance R, and the counter electromotive voltage E by calculation of V = Ia × R + E.
The controller 9 feedback-controls the field current Ifh of the generator 8 so that the generated voltage of the generator 8 becomes the target voltage V thus obtained.

In addition to the control of the generator 8 and the electric motor 4, the four-wheel drive controller 9 obtains an allowable upper limit torque line to be used when limiting the motor torque command value tTm in step S14 of FIG. 3 using the control program of FIG.
First, in step S21, it is checked whether or not the vehicle speed VSP is in a low vehicle speed range in which four-wheel drive by the electric motor 4 should be permitted. If the vehicle speed VSP is not in the four-wheel drive permitted vehicle speed region, control of the electric motor 4 is unnecessary. Therefore, the control is terminated as it is.

When it is determined in step S21 that the vehicle speed VSP is within the four-wheel drive permitted vehicle speed range, in step S22, the motor rotational acceleration (d / dt) Nm that can be obtained by differentiation of the motor rotational speed Nm, that is, the vehicle acceleration is shown in FIG. It is checked at some point on the output possible upper limit torque line whether or not it is equal to or higher than the abnormal voltage increase determination acceleration for determining whether the output possible upper limit torque causes a sudden decrease that causes the abnormal voltage increase.
In the case of the output possible upper limit torque line in Fig. 10, the change rate of the output possible upper limit torque with respect to the motor rotation speed Nm is the largest in the motor rotation speed range of Nm1 to Nm2, and this is the most likely to cause an abnormal voltage increase. It is preferable to determine the above abnormal voltage rise determination acceleration as a reference.

  If it is not determined in step S22 that the motor rotational acceleration (d / dt) Nm, that is, the vehicle acceleration is equal to or higher than the abnormal voltage rise determination acceleration, the present invention does not cause a problem to be solved, so the control is terminated as it is. Then, the motor torque command value tTm is limited (step S14 in FIG. 3) based on the output possible upper limit torque line illustrated in FIG.

However, if it is determined in step S22 that the motor rotational acceleration (d / dt) Nm, that is, the vehicle acceleration is equal to or higher than the abnormal voltage rise determination acceleration, the problem to be solved by the present invention arises. Proceeding to S23, the virtual upper limit motor torque is set as follows, and the allowable upper limit torque line is obtained.
In other words, as shown by the solid line in FIG. 5 in which the output possible upper limit torque line in FIG. The virtual upper limit motor torque is set by changing the characteristics in the several ranges Nm1 to Nm2 to characteristics having a gradual change rate, and the allowable upper limit torque line that is the same as the output possible upper limit torque line is obtained for the other characteristics.

  Thus, in this embodiment, when the motor torque command value tTm is limited in step S14 of FIG. 3, instead of the output possible upper limit torque line shown in FIG. 10, the allowable upper limit torque line shown in FIG. The motor torque command value tTm is limited.

Therefore, in this embodiment, even when it is determined in step S22 that the motor rotational acceleration (d / dt) Nm, that is, the vehicle acceleration is equal to or higher than the abnormal voltage increase determination acceleration, the motor torque command value tTm has a gentle slope. 5 is limited along the virtual upper limit motor torque line in FIG. 5, and the decrease in the motor torque command value tTm accompanying the increase in the motor rotation speed Nm (vehicle speed VSP) becomes moderate.
For this reason, while the motor torque command value tTm is being limited, it is possible to mitigate the decrease rate becoming so steep that an abnormal voltage increase occurs. An adverse effect on the control system of the wheel drive vehicle can be avoided, and the troublesome operation of the safety device for preventing this adverse effect can be eliminated.

By the way, the speed at which the motor torque command value tTm is reduced during the above-described limit, that is, the extent to which an abnormal voltage rise occurs, becomes more significant as the motor rotational acceleration (d / dt) Nm, that is, the vehicle acceleration increases.
Therefore, in order to slow down the motor torque command value tTm during the restriction and prevent the voltage from rising abnormally, the low gradient virtual upper limit motor torque line set as shown in FIG. 5 is the motor rotational acceleration (d / dt ) It is better to make the gradient gentler as Nm, that is, the vehicle acceleration increases.

  In this sense, if only one virtual upper limit motor torque line is set as shown in FIG. 5, the gradient of the virtual upper limit motor torque line is appropriate only when the motor rotational acceleration (d / dt) Nm corresponding to a specific vehicle acceleration is set. However, when the motor rotational acceleration (vehicle acceleration) is larger than this, the rate of decrease of the motor torque command value tTm during the limitation is not sufficiently slow, and it is not possible to reliably prevent an abnormal increase in voltage. When the motor rotational acceleration (vehicle acceleration) is smaller than this, the rate of decrease of the motor torque command value tTm during the above limit is slower than necessary, and even though the abnormal increase in voltage can be prevented, unnecessary motor torque 4-wheel drive performance is degraded due to the restriction of the command value tTm.

FIG. 6 and FIG. 7 show another embodiment of the present invention which can solve the problem concerning this point.
In this embodiment, in steps S21 and S22 in FIG. 6, the same determination as in the step indicated by the same reference numeral in FIG. 4 is performed, and in step S21, the vehicle speed VSP is determined to be outside the four-wheel drive permitted vehicle speed range. Alternatively, when it is determined in step S22 that the motor rotational acceleration (d / dt) Nm, that is, the vehicle acceleration is less than the abnormal voltage increase determination acceleration, the same processing as in FIG.
If it is determined in step S21 that the vehicle speed VSP is within the four-wheel drive permitted vehicle speed range, and it is determined in step S22 that the motor rotational acceleration (d / dt) Nm, that is, the vehicle acceleration is greater than or equal to the abnormal voltage increase determination acceleration, Is advanced to step S24 instead of step S23 in FIG. 4, the virtual upper limit motor torque is set as follows, and the allowable upper limit torque line is obtained.

  That is, as shown by the solid line and the two-dot chain line in FIG. 7 where the output possible upper limit torque line in FIG. 10 is transferred as a wavy line, the change rate of the output possible upper limit torque with respect to the motor rotation speed Nm is the largest, and the abnormal voltage rises. Change the characteristic of the motor rotation speed range Nm1 to Nm2 that is likely to occur to the motor rotation acceleration (d / dt) Nm, that is, the characteristic with a gradual change rate according to the vehicle acceleration, and set the virtual upper limit motor torque. The allowable upper limit torque line having the same characteristics as the output possible upper limit torque line is obtained.

  As is apparent from FIG. 7, the virtual upper limit motor torque is set such that the larger the motor rotational acceleration (d / dt) Nm, the more gradual the change with respect to the motor rotational speed Nm, and preferably the motor rotational speed Nm. The rate of change of the virtual upper limit torque with respect to the motor torque acceleration value (d / dt) Nm, and the rate of decrease of the motor torque command value tTm due to the limitation of the motor torque command value tTm based on the virtual upper limit torque Determine the fastest rate of decrease in a range that does not cause an abnormal rise.

  Thus, in the present embodiment, when the motor torque command value tTm is limited in step S14 of FIG. 3, a diagram corresponding to the motor rotational acceleration (d / dt) Nm is used instead of the output possible upper limit torque line shown in FIG. 7 limits the motor torque command value tTm based on the allowable upper limit torque line indicated by a solid line or any two-dot chain line.

Therefore, in this embodiment, even when it is determined in step S22 that the motor rotational acceleration (d / dt) Nm, that is, the vehicle acceleration is equal to or higher than the abnormal voltage increase determination acceleration, the motor torque command value tTm has a gentle slope. 7 is limited along the virtual upper limit motor torque line in FIG. 7, and the decrease in the motor torque command value tTm accompanying the increase in the motor rotation speed Nm (vehicle speed VSP) becomes moderate.
For this reason, while the motor torque command value tTm is being limited, it is possible to mitigate the decrease rate becoming so steep that an abnormal voltage increase occurs. An adverse effect on the control system of the wheel drive vehicle can be avoided, and the troublesome operation of the safety device for preventing this adverse effect can be eliminated.

Moreover, in this embodiment, as shown in FIG. 7, the gradient of change of the virtual upper limit motor torque line with respect to the motor rotational speed Nm is set more gradually as the motor rotational acceleration (d / dt) Nm is larger. The rate of change of the virtual upper limit torque with respect to the rotational speed Nm is expressed as the voltage decrease rate of the motor torque command value tTm due to the above limitation of the motor torque command value tTm based on the virtual upper limit torque for each motor rotational acceleration (d / dt) Nm. Because it was decided to be the fastest rate of decrease in a range that does not cause an abnormal rise of
Under any motor rotation acceleration (d / dt) Nm, the slope of the virtual upper limit motor torque line becomes appropriate,
When the motor rotation acceleration (vehicle acceleration) is large, the rate of decrease of the motor torque command value tTm during the above limit is not slow enough to reliably prevent abnormal voltage rise.
When the motor rotation acceleration (vehicle acceleration) is small, the speed of the motor torque command value tTm during the above limit is slower than necessary, and the unnecessary limit of the motor torque command value tTm causes a decrease in four-wheel drive performance. Can be avoided.

  By the way, in each of the above embodiments, after the motor rotational acceleration (d / dt) Nm, that is, the vehicle acceleration is increased, a virtual upper limit motor torque line having a low gradient is set to obtain an allowable upper limit torque line. In this case, acceleration from the increase operation of the accelerator opening APO (in some cases, the operation of increasing the accelerator opening APO after switching the automatic transmission 5 to the acceleration range) until the actual acceleration of the vehicle occurs. The above-described effects cannot be expected during response delay.

FIG. 8 and FIG. 9 show still another embodiment of the present invention which can solve the problem concerning this point.
Therefore, in this embodiment, as in the above embodiments, after the motor rotational acceleration (d / dt) Nm, that is, the vehicle acceleration has increased, a hypothetical upper limit motor torque line with a low gradient is set and the allowable upper limit torque line is set. In addition, the virtual upper limit motor torque line with a low gradient is set in response to the driver's acceleration request.
In addition to steps S21, S22, and S24 similar to those in FIG. 6, steps S25 and S26 are provided.

In this embodiment, in steps S21 and S22 in FIG. 8, the same determination as in the steps indicated by the same reference numerals in FIGS. 4 and 6 is performed.
If it is determined in step S21 that the vehicle speed VSP is not within the four-wheel drive permitted vehicle speed range, the same processing as in FIGS. 4 and 6 is performed,
If it is determined in step S21 that the vehicle speed VSP is within the four-wheel drive permitted vehicle speed range, and it is determined in step S22 that the motor rotational acceleration (d / dt) Nm, that is, the vehicle acceleration is greater than or equal to the abnormal voltage increase determination acceleration, In S24, the virtual upper limit motor torque is set by the same processing as in the steps indicated by the same reference numerals in FIG.

In step S22, which is selected when it is determined in step S22 that the motor rotational acceleration (d / dt) Nm, that is, the vehicle acceleration is not equal to or higher than the abnormal voltage increase determination acceleration, whether or not there is a vehicle acceleration request from the driver. Check.
In this check, the acceleration request of the vehicle is made by increasing the amount of depression of the accelerator pedal (accelerator opening APO) corresponding to the required load command means of the engine 2, and in some cases, the automatic transmission 5 is turned on. Since the acceleration request is made by increasing the accelerator opening APO after switching to the acceleration range, the increase time change rate ΔAPO of the accelerator opening APO and a combination of this and the acceleration range switching operation of the automatic transmission 5 are combined. To check for acceleration request.

  If it is determined in step S25 that there is no acceleration request, the control is terminated as it is and the virtual upper limit motor torque is not set, so that the motor rotational acceleration (d / dt) Nm is abnormal in step S22 of FIGS. Similar to the case where it is determined that the acceleration is less than the voltage increase determination acceleration, the motor torque command value tTm in step S14 in FIG. 3 is limited based on the output possible upper limit torque line in FIG.

However, if it is determined in step S25 that there is an acceleration request, control proceeds to step S26, the virtual upper limit motor torque is set as follows, and an allowable upper limit torque line is obtained.
In other words, as shown by a solid line and a two-dot chain line in FIG. 9 where the output possible upper limit torque line of FIG. 10 is transferred as a wavy line, the change rate of the output possible upper limit torque with respect to the motor rotation speed Nm is the largest, and the abnormal voltage rises. This acceleration requirement (ΔAPO, VSP) is large according to the acceleration requirement (ΔAPO, VSP) of the vehicle that can be seen from the increase speed ΔAPO of the accelerator opening APO and the vehicle speed VSP with the characteristics of the motor speed range Nm1 to Nm2 that are likely to occur The virtual upper limit motor torque is set by changing to a characteristic with a gentle change rate, and an allowable upper limit torque line having the same characteristics as the output possible upper limit torque line is obtained for the other characteristics.

  Note that the virtual upper limit motor torque is set so that the change with respect to the motor rotation speed Nm becomes gentler as the acceleration request degree (ΔAPO, VSP) of the vehicle is larger as described above and as is apparent from FIG. Preferably, at this time, the rate of change of the virtual upper limit torque with respect to the motor rotation speed Nm is set to a motor based on the virtual upper limit torque for each acceleration request degree (ΔAPO, VSP) of the vehicle (actually, for each vehicle acceleration achieved thereby). The reduction rate of the motor torque command value tTm due to the limitation of the torque command value tTm is determined so as to be the fastest reduction rate in a range where the above-described abnormal voltage increase does not occur.

  Thus, in this embodiment, when the motor torque command value tTm is limited in step S14 of FIG. 3, the output of FIG. 10 can be output from the time when the acceleration response is delayed until the acceleration is actually performed after the accelerator pedal is depressed. Instead of the upper limit torque line, the motor torque command value tTm is limited based on the allowable upper limit torque line shown by the solid line or any two-dot chain line in FIG. 9, and the motor torque command value tTm decreases during this limit. It is possible to mitigate the fact that the speed becomes steep enough to cause an abnormal voltage increase, and it is possible to avoid an adverse effect on the control system of the electric motor type four-wheel drive vehicle due to the abnormal voltage increase. The troublesome operation of the safety device for preventing it can be eliminated.

Furthermore, as shown in FIG. 9, the change gradient of the virtual upper limit motor torque line with respect to the motor rotational speed Nm is set more gently as the vehicle acceleration requirement degree (ΔAPO, VSP) is larger, and preferably, with respect to the motor rotational speed Nm. The rate of change of the virtual upper limit torque is determined for each acceleration request (ΔAPO, VSP) of the vehicle, and the rate of decrease in the motor torque command value tTm due to the above limitation of the motor torque command value tTm based on the virtual upper limit torque increases abnormally. Since it was decided to be the fastest rate of decrease in a range that does not cause
Under any vehicle acceleration requirement (ΔAPO, VSP), the slope of the virtual upper limit motor torque line is appropriate,
When the acceleration demand of a large vehicle (ΔAPO, VSP), the rate of decrease of the motor torque command value tTm during the above limit is not slow enough to prevent the abnormal increase in voltage reliably.
When the acceleration requirement of a small vehicle (ΔAPO, VSP), the speed of decrease in the motor torque command value tTm during the above limit is slower than necessary, and the unnecessary motor torque command value tTm limits the four-wheel drive performance. The problem of causing a decrease can be avoided.

In this embodiment, while the vehicle is actually accelerated after a delay in acceleration response, step S22 in FIG. 8 advances control to step S24, and processing similar to the step indicated by the same reference numeral in FIG. As shown in FIG. 7, to set the virtual upper limit motor torque indicated by the solid line or any two-dot chain line according to the motor rotational acceleration (d / dt) Nm, to obtain the allowable upper limit torque line as shown in FIG.
When the motor torque command value tTm is limited in step S14 in FIG. 3, the solid line in FIG. 7 corresponding to the motor rotational acceleration (d / dt) Nm or either Needless to say, the motor torque command value tTm is limited based on the allowable upper limit torque line indicated by the dotted line, and the same effects as described above with reference to FIGS. 6 and 7 can be obtained.

1 is a schematic diagram illustrating a drive control system of an electric motor type four-wheel drive vehicle including a motor drive control device according to an embodiment of the present invention. It is a flowchart which shows the engine surplus torque calculation program which the four-wheel drive controller in the drive control system of the motor four-wheel drive vehicle performs. It is a flowchart which shows the control program of the generator and motor which the same 4 wheel drive controller performs. It is a flowchart which shows the motor permissible upper limit torque line calculation program which the four-wheel drive controller performs. FIG. 5 is a characteristic diagram showing a motor allowable upper limit torque line obtained by the calculation program of FIG. 6 is a flowchart showing a motor allowable upper limit torque line calculation program instead of FIG. 4, showing a motor drive control device according to another embodiment of the present invention. FIG. 7 is a characteristic diagram showing a motor allowable upper limit torque line obtained by the calculation program of FIG. FIG. 7 is a flowchart showing a motor allowable upper limit torque line calculation program instead of FIG. 6, showing a motor drive control device according to still another embodiment of the present invention. FIG. 9 is a characteristic diagram showing a motor allowable upper limit torque line obtained by the calculation program of FIG. It is a characteristic diagram which shows the general output possible upper limit torque line of an electric motor.

Explanation of symbols

1L front left wheel (main drive wheel)
1R right front wheel (main drive wheel)
2 Engine (Main power source)
3L left rear wheel (electric motor drive wheel)
3R right rear wheel (electric motor drive wheel)
4 Rear wheel drive motor (electric motor)
5 Automatic transmission 6 Differential gear device 7 Endless belt 8 Generator 9 Four-wheel drive controller
10 Power line
11 Relay
12 Reducer
13 4WD clutch
14 Differential gear unit
21 Four-wheel drive switch
22 Wheel speed sensors
23 Motor rotation sensor
25 Accelerator position sensor

Claims (5)

A main drive wheel driven by power from a main power source;
An electric motor drive wheel driven by power from an electric motor that responds to power generated by a generator coupled to the main power source,
In the electric motor type four-wheel drive vehicle that limits the motor torque command value of the electric motor so as not to exceed the output possible upper limit torque for each motor rotation speed,
When the rate of decrease in the motor torque command value due to the limitation of the motor torque command value is a rapid decrease that causes an abnormal increase in voltage due to the surplus of the generated power, the output possible upper limit for the motor rotation speed An electric motor type four-wheel drive vehicle configured to limit the motor torque command value by using a virtual upper limit torque having a gentler change rate than a torque change rate instead of the output possible upper limit torque. Motor drive control device. The motor drive control device for an electric motor type four-wheel drive vehicle according to claim 1,
A motor drive control device for an electric motor type four-wheel drive vehicle, characterized in that the rate of change of the virtual upper limit torque with respect to the motor rotational speed is made gentler as the rate of change of the motor rotational speed increases. In the motor drive control device of the electric motor type four-wheel drive vehicle according to claim 2,
The rate of change of the virtual upper limit torque with respect to the motor rotational speed is set to the rate of decrease in the motor torque command value due to the limitation of the motor torque command value based on the virtual upper limit torque for each rate of increase in motor rotational speed. A motor drive control device for an electric motor type four-wheel drive vehicle, characterized in that it has been determined to have the fastest rate of decrease within a range in which no abnormal increase in voltage occurs. In the motor drive control device of the electric motor type four-wheel drive vehicle according to any one of claims 1 to 3,
An electric motor type four-wheel vehicle characterized in that the rate of change of the virtual upper limit torque with respect to the motor rotational speed is made gentler as the rate of change in the required load increase time of the main power source by the required load command means of the main power source increases. Motor drive control device for driving vehicle. In the motor drive control device of the electric motor type four-wheel drive vehicle according to claim 4,
The rate of change of the virtual upper limit torque with respect to the motor rotational speed is the rate of decrease in the motor torque command value due to the limitation of the motor torque command value based on the virtual upper limit torque for each required load increase time change rate of the main power source. However, the motor drive control device for an electric motor type four-wheel drive vehicle is determined so as to achieve the fastest decrease speed in a range in which the voltage does not increase abnormally.

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